1. Field of the Invention
The present invention relates to a method and an apparatus for operating a direct injection (inside each cylinder) type internal combustion engine. In particular, the method and apparatus of the present invention are suitable for the operation of spark-ignition direct injection (DI) type engines.
2. Description of the Related Art
When a spray of fuel or vapor is to be ignited by a spark plug in an internal combustion engine, an optimum air-fuel mixture must be produced in the vicinity of the spark gap within the very short time that the spark is maintained, and this is difficult to achieve under all operating conditions. In other words, because of the various operating conditions occurring in an engine, a stable air-fuel mixture cannot always be formed in the vicinity of the spark gap at the proper ignition timing, resulting in unreliable ignition of the fuel or vapor.